Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate or workpiece, and patterning the various layers using lithography to form circuit components and elements thereon.
The upper material layers of semiconductor devices typically comprise metallization layers that are used to interconnect various electrical devices and elements formed on an integrated circuit (IC). The metallization layers are typically formed in a back end of line (BEOL) of a semiconductor manufacturing process, for example. However, the lower layers of semiconductor devices do not typically contain metal, because some metals may contaminate semiconductive materials in some applications. The fabrication of lower levels of semiconductor devices that do not contain metal are often referred to as a front end of line (FEOL) of a semiconductor manufacturing process, for example. Structures that are referred to in the art as “sinker contacts” are often used to make electrical connection in the FEOL to devices formed on a semiconductor workpiece or substrate comprising a conductive buried layer, for example.
Sinker contacts are formed by implanting dopants into a substrate, and annealing or heating the substrate to drive the dopants deeper into the substrate. The dopants make the semiconductive material conductive, and thus sinker contacts may be used to make electrical contact to conductive buried layers in the substrate. However, since the lateral diffusion width is on the order of the vertical diffusion depth, conventional sinker contacts are typically quite large, comprising a width of tens of μm or greater in some applications, for example, requiring a large amount of real estate on an IC, which is costly and limits the amount that a semiconductor device may be scaled down in size. For example, to provide electrical contact to a 5 μm deep buried layer, a total sinker contact width after out-diffusion is typically on the order of about 15 μm, which is quite large in comparison to today's state of the art minimum semiconductor structures that may have a total width of less than about 100 nm.
Thus, what are needed in the art are improved sinker contacts for semiconductor devices and methods of manufacture thereof.